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Phillip A. Wadl, Livy H. Williams III, Matthew I. Horry, and Brian K. Ward

the wireworm-cucumber beetle-flea beetle (WDS) severity index ( Chalfant et al., 1990 ). This complex of insect pests consists of several species of wireworms (e.g., Melanotus communis and Conoderus sp.), banded and spotted cucumber beetles

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J.M. Schalk, J.R. Bohac, P.D. Dukes, and W.R. Martin

This 2-year study was conducted to determine if soil insect damage could be reduced in sweetpotato [Ipomoea batatas (L.) Lam] by treatment with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae Weiser), in conjunction with sweetpotato cultivars that differed in susceptibility to soil insect damage. Analysis of field data for the first year showed that the parasitic nematode provided significant damage protection of sweetpotato from wireworms (Conoderus spp.), Diabrotica sp., Systena sp., and sweetpotato flea beetle (Chaetocnema confinis Crotch), but not from grubs (Plectris aliena Chapin; Phyllophaga ephilida Say). In this same test, fonofos used alone provided protection against wireworm-Diabrotica-Systena (WDS complex) damage. In the second test, the nematode did not provide soil insect protection for the WDS complex, but fonofos did reduce damage for these insects. Poor efficacy in the second test with the nematode probably was due to high rainfall, which saturated the soil. Resistant cultivars provided good protection for all three categories of damage. When used with the insect-susceptible check `SC 1149-19', the nematode or fonofos treatments provided better control for all insect categories in the first test. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with the nematode and/or fonofos treatment (64% higher crop protection than the susceptible check line). Chemical name used: O-ethyl-S-phenylethylphosphonodithioate [fonofos (Dyfonate 10G)].

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James M. Schalk, Alfred Jones, Philip D. Dukes, and Kenneth P. Burnham

This study was designed to determine if the preference of soil insects for sweetpotato [Ipomoea batatas (L.) Lam.] cultivars is affected by the proximity of resistant or susceptible plant cultivars at various spacings. Comparisons were made for damage caused by wireworms (Conoderus spp.), Diabrotica spp., Systena spp., sweetpotato flea beetles (Chaetocnema confinis Crotch), and grubs (Plectris aliena Chapin; Phyllophaga ephilida Say) in previously reported resistant and susceptible cultivars. Field plots were planted with a resistant cultivar, a susceptible cultivar, or the two cultivars intermixed. Large roots exhibited more insect damage than medium and small roots. When plant spacing was increased, roots were larger and insect damage more severe. Mixed plantings of resistant and susceptible cultivars significantly reduced insect damage in the susceptible plants. Planting regime did not influence insect damage for the resistant cultivars.

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Paul G. Thompson, John C. Schneider, Boyett Graves, and Edward E. Carey

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Srijana Shrestha and Carol Miles

), sweetpotato flea beetle ( Chaetocnema confinis ), elongate flea beetle ( Systena elongata ), wireworm larvae ( Conoderus sp.), white grub larvae ( Phyllophaga sp. and Plectris aliena ), sugarcane beetle ( Euetheola rugicepes ), and sweetpotato weevil

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Barbara J. Daniels-Lake, Robert K. Prange, Sonia O. Gaul, Kenneth B. McRae, Roberto de Antueno, and David McLachlan

recommendation, to control an exceptional outbreak of wireworm that had seriously damaged the potato crop in previous years. The association of OFO with γ-CHC was not definitive, however, because 5 of the 13 potato samples most severely affected by OFO were grown

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James M. Schalk, Philip D. Dukes, Alfred Jones, and Robert L. Jarret

The reactions of eight sweetpotato [Ipomoea batatas (L.) Lam.] introductions were categorized for root damage by wireworms, Diabrotica sp., Systena sp. (WDS), sweetpotato flea beetle (SPFB), and grubs. Clones were compared with resistant (`Regal') and susceptible (`SC-1149-19') entries. The number of resistant clones for the WDS, SPFB, and grubs were three, four, and one, respectively, intermediate five, four, and one, and susceptible zero, zero, and six, respectively. This test demonstrated that significant levels of soil insect resistance exist in these sweetpotato introductions for use by plant breeders.

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J. M. Schalk, A. Jones, P. D. Dukes, and D. R. Seal

The test involved the use of a control (untreated), an entomopathogenic nematode (Steinernema carpocapsae), a granular insecticide (Dyfonate 2.24 Kg ai/ha) in combination with 7 sweetpotato cultivars having varying levels of resistance and susceptibility to soil insect damage. The parasite was applied three times at monthly intervals (67/cm2). The parasite or insecticide did not reduce root injury by soil insects as compared to the control (untreated). Wireworms, Diabrotica sp. and Systena sp. damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultivars (SC–1149-19, Jewel and Centennial). Sweetpotato flea beetle resistance was observed for all cultivars except SC–1149-19 which was susceptible. In this test resistant cultivars were more effective in reducing soil insect damage than the biological or chemical control methods.

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J.K. Peterson and D.M. Jackson

Resin glycosides extracted from sweetpotato skins were bioassayed for their effects on survival, development, and fecundity of diamondback moths, Plutella xylostella (L.). Glycosides were incorporated into an artificial diet (Bio-Serv, Inc.) and fed to diamondback larvae. Neonatals were individually fed artificial diet with 0.00, 0.25, 0.50, 1.00, 1.50, and 2.00 mg·mL-1. There were highly significant negative correlations between glycoside levels and survival as well as weight of survivors after 6 days. A significant positive relationship existed between dosages and development time. Lifetime fecundity was negatively affected at sublethal doses. The glycosides are viewed as contributors to resistance to the wireworm, Diabrotica and Systena insect complex.

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J. M. Schalk, A. Jones, P. D. Dukes, and D. R. Seal

The test involved the use of a control (untreated), an entomopathogenic nematode (Steinernema carpocapsae), a granular insecticide (Dyfonate 2.24 Kg ai/ha) in combination with 7 sweetpotato cultivars having varying levels of resistance and susceptibility to soil insect damage. The parasite was applied three times at monthly intervals (67/cm2). The parasite or insecticide did not reduce root injury by soil insects as compared to the control (untreated). Wireworm, Diabrotica and Systena damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultvars (SC–1149-19, Jewel and Centennial). Sweetpotato flea beetle resistance was observed for all cultivars except SC–1149-19 which was susceptible. In this test resistant cultivars were more effective in reducing soil insect damage than the biological or chemical control methods.